1. Field of the Invention
This invention relates to a zoom lens for use in a single-lens reflex camera, an electronic still camera or the like, and in particular to a zoom lens of positive-negative-positive-positive four-group construction whose maximum angle of view includes a wide angle of view of 60.degree. or greater and whose zoom ratio is of the order of three times.
2. Related Background Art
There are known numerous zoom lenses of positive-negative-positive-positive four-group construction coveing a maximum angle of view of 60.degree. and having a zoom ratio of the order of three times, and one of such zoom lenses is proposed, for example, in the applicant's U.S. Pat. No. 4,699,475. Also, a zoom lens of such four-group construction in which a second lens group comprises, in succession from the object side, a negative lens, a negative lens and a cemented positive lens consisting of a positive lens and a negative lens is disclosed in Japanese Laid-Open Patent Application No, 58-202417.
In the embodiments of the former, i.e., U.S. Pat. No. 4,699,475, the number of lens components is as great as 15 to 16 and therefore, it is difficult for such a zoom lens to be inexpensively supplied as a zoom lens for common use in a single-lens reflex camera. Further, the total thickness of a second lens group is as great as 15.5 mm and therefore, to secure a zoom ratio amounting even to three times, the spacing between a first lens group and a third lens group must be secure sufficiently. As a result, the full length of the lenses the wide angle end amounts even to 130 mm and therefore, this zoom lens is bulky to carry a zoom lens for common use and can hardly be said to be preferable.
Also, in the latter, i.e., Japanese Laid-Open Patent Application No. 58-202417, the zoom ratio amounts even to 3.8 times and moreover, the total thickness of a second lens group is held down to the same degree as the former, and compactness to the full length is achieved for the zoom ratio. However, when zooming is effected from the wide angle end to the telephone end, chromatic aberration, particularly spherical aberration of g-line (435.8 nm), fluctuates greatly from over-corrected state to under-corrected state, and this leads to the problem that particularly when fully open aperture photographing is done by the use of black-and-white film, the image will be greatly deteriorated.
This is not limited in the lens disclosed in 1 Japanese Laid-Open Patent Application No. 58-202417, but any conventional zoom lens in which a second lens group comprises, in succession from the object side, a negative lens, a negative lens and a positive cemented lens consisting of a positive lens and a negative lens cemented together has suffered from the problem that the spherical aberration of g-line at the telephoto end is under-corrected.
Also known are numerous zoom lenses of positive-negative-positive-positive four-group construction including a maximum angle of view of 60.degree. and having a zoom ratio of the order of three times in which a second lens group comprises, in succession from the object side, a negative lens, a cemented negative lens and a positive lens, and for example, Japanese Laid-Open Patent Application No. 57-192918 is known.
However, again in the zoom lens disclosed in this Japanese Laid-Open Patent Application No. 57-192918, the number of lens components is great and it is difficult for this zoom lens to be ineXpensively provided as a zoom lens for a single-lens reflex camera. Further, the full length of the lens at the wide angle is as great as 143 mm, which also poses a problem in portability.